To create .jar files eclipse has that very nice "JarPackager" that creates .jardesc files containing the list of files and directories and other instructions for the creation of a .jar file. Can one use that description somehow with an automatic builder?

I find it kind of odd, that one has to respecify most of that info when creating a build.xml file for ant while one could easily pick and select all the required info using JarPackager. Or is there an ant-task that essentially just "executes" .jardesc files?